Tag Archives: earthquake

New study shows that Antarctica is seismically active — we just haven’t listened close enough

Long thought to be seismically silent, Antarctica is actually quite active, though its earthquakes can be very difficult to detect.

An installation of one of the monitors in the East Antarctica seismic array. Image credits: Amanda Lough.

The first Antarctic earthquake was detected in 1982, and since then, only 8 other earthquakes had ever been observed. That all changed in 2009, when a team including Amanda Lough — then a student but now an assistant professor at Drexel University — installed the first winter-through-summer seismic array in Antarctica: 27 earthquakes were detected in the first year alone.

Before this, many geologists thought Antarctica was exceptionally stable, and essentially inactive seismically. But this newly installed array showed that we just weren’t watching closely enough. Now, scientists have presented the results in a new study.

“Ultimately, the lack of recorded seismicity wasn’t due to a lack of events but a lack of instruments close enough to record the events,” explained Lough, who is the lead author on a study discussing the array’s results in Nature Geoscience.

It makes a lot of sense to think that Antarctica is seismically silent. East Antarctica lies on a so-called “craton” — an old and generally stable part of the Earth’s lithosphere. Cratons are generally found in the interiors of tectonic plates and feature ancient basement rock.

But even so, the seismic silence of Antarctica was considered a bit suspicious.

The bedrock topography of Antarctica, via NASA.

There were several theories attempting to explain this conspicuous silence. Among these theories, some geologists assumed that the ice covering Antarctica was acting like an insulating blanket, muffling the seismic waves. However, the new recordings now show that this isn’t the case: it’s just that we didn’t have an array close enough.

Not having an array wasn’t for lack of motivation, though. Setting up a seismic array is no easy feat, especially in the frigid, unforgiving environment of Antarctica. Lough and her colleagues had to fly from point to point, often digging their own runways, and placing the recording equipment. The work was hard, the flight was packed, and it took a lot of perseverance and determination — but at the end of the day, it was worth it.

The bedrock topography of Antarctica, via NASA.

Installing the sensors was not the easiest thing. Image credits: Amanda Lough.

The monitored earthquakes aren’t big (with magnitudes between 2.1 and 3.9), but they offer an unprecedented view into Antarctica’s subsurface. Most of the earthquakes happened around an area called the Gumburtsev Subglacial Mountains, which Lough and others believe are part of an ancient continental rift system, somewhat similar to the East African Rift, but much older.

[panel style=”panel-info” title=”Rift” footer=””]The Earth’s crust is made of tectonic plates. These rigid plates glide over the mantle, moving at speeds of a few centimeters per year. That might not seem like much but over geological periods (millions and millions of years), these movements can dramatically change the surface of the planet.

In some areas, plates are crashing into each other (convergent boundary), and in other areas, they move away from each other (divergent boundary). Rifts form at divergent boundaries. The most famous example is the East African Rift, which is bordered by a series of mountains and active volcanoes.[/panel]

A depiction of the Reelfoot Rift. Image credits: USGS.

It’s no surprise then that most of the earthquakes take place around the rift.

“There is a study we cite in the paper that shows that more than 52 percent of seismic events in continental areas occur in rifted crust, so it’s not unexpected that we see the correlation here,” Lough said.

“The rifts provide zones of weakness that enable faulting to occur more easily, and it may be that the situation here is such that activity is occurring preferentially along these areas of preexisting weakness,” Lough said, though she emphasized “we only have one year of data” and more needs to be observed before they have a “full picture.”

Researchers observed very few earthquakes outside of these rift zones.

While these earthquakes don’t make much of a difference for Antarctica’s inhabitants (which are mostly penguins, seals, and coastal seabirds), it’s an important piece of the geological puzzle we call Earth. It also shows that if you want to understand something, you really need to study it.

“Antarctica is the least-instrumented continent, but other areas of the globe also lack sufficient instrumentation,” Lough said. “There are some obvious holes in coverage in the Global Seismic Network. For example, the ocean covers 71 percent of the planet, but it is expensive and very difficult to get instruments there. We need to think about improving coverage and then improving the density of it.”

The study has been published in Nature Geoscience.

Seismology could soon be used to protect elephants from poachers

An innovative approach could help monitor elephants using earthquakes, and even protect them from poachers.

This image shows an African elephant with a visualization of the vibrations it generates, which can be used to determine its behavior. Image credits: Robbie Labanowski.

A story of elephants and earthquakes

As undergrads, we used to analyze open data from some seismographs in the city. Some were old and picked up a lot of noise and, on one of them, there was a strange wave that appeared every 10 minutes or so. It was too regular to be earthquake-related and, as it turns out, it was the local subway. Just like earthquakes, other things can generate waves that can be picked up by seismological equipment — in this case, it’s elephants.

In a new study, researchers describe how seismology could be used to track the movement of elephants, as well as their vocalizations.

The results seem to back the theory that elephants use ground vibrations for long-distance communications, but it’s surprising to see just how strong these vibrations really are.

“We were surprised by the size of the forces acting on the ground that were generated by elephants when they vocalize,” says Beth Mortimer of the Universities of Oxford and Bristol, UK. “We found that the forces generated through elephant calls were comparable to the forces generated by a fast elephant walk. This means that elephant calls can travel significant distances through the ground and, in favorable conditions, further than the distance that calls travel through the air.”

Mortimer focuses on animals that use vibrations to communicate between themselves — previously, she studied spiders and their webs but now, she’s moved to a bigger target. She believes that conservationists could ultimately design an alarm system using elephant-generated vibrations as a trigger.

Along with Will Rees, a Masters student, she recorded vibrations generated by wild elephants in Kenya while they displayed different behaviors, including walking and calling. They wanted to see how far elephant-generated vibrations travel and how they are affected by the terrain type and human noise.

They found that, under ideal conditions, the vibrations can be picked up from several kilometers away, but this varies greatly on the type of terrain and existing noise. A surprising result they gathered was that human noise can actually be very disruptive for the elephant calls — in other words, humans interfere with the elephants’ ability to communicate with each other over great distances.

But when the seismological receivers were close enough, they could be used to not only detect elephants, but also monitor their behavior and assess when they are threatened by poachers.

“We suggest that monitoring ground-based vibrations can be used in a practical context to not only detect elephants, but determine their behaviors,” Mortimer says. “Using multiple seismic recorders in remote locations, we suggest that detection, location, and classification algorithms can be generated that allow monitoring of elephants in real-time.”

However, before this can be realistically achieved, much more experimental data needs to be gathered and refined. Geophysicist Tarje Nissen-Meyer at the University of Oxford, UK, who was also involved in the study, wants to set up a larger, long-term network of seismic sensors. Along with aerial, visual, and acoustic surface sensors, a seismic network might also offer valuable information and alert park rangers when elephants are in trouble.

“We hope to build on these initial findings to develop a comprehensive approach for monitoring and understanding the behavior of large mammals in these pristine, changing, and fragile environments,” Nissen-Meyer says.

The study “Classifying elephant behaviour through seismic vibrations”, by Mortimer et al., has been published in Current Biology:  https://www.cell.com/current-biology/fulltext/S0960-9822(18)30420-2

Illustration of NASA's InSight quake-monitoring lander. Credit: NASA.

NASA lander will study ‘Marsquakes’

Illustration of NASA's InSight quake-monitoring lander. Credit: NASA.

Illustration of NASA’s InSight quake-monitoring lander. Credit: NASA.

NASA is gearing up for one of its most anticipated launches of the year. On Saturday, a one-of-a-kind Mars explorer called InSight is destined to launch for the Red Planet. Its mission: to study the slight rumbles and tremors produced as the planet wobbles. Just like ‘earthquakes’, these are ‘marsquakes’ — and whatever waves the lander’s instruments will pick up might help scientists gain unprecedented insights about Mars’ interior, from its crust to its very core.

“How we get from a ball of featureless rock into a planet that may or may not support life is a key question in planetary science,” said Bruce Banerdt, InSight principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’d like to be able to understand what happened.”

Like earthquakes, marsquakes are vibrations of the ground. However, while an earthquake is produced by the movement of tectonic plates, scientists believe that marsquakes occur when the planet cools and contracts, causing the crust to ruck up slightly. Scientists believe that all planetary bodies experience quakes, ranging from those that vibrate fast to those that rumble low. In the 1970s, NASA’s Viking lander tried to measure quakes on Mars but its instruments weren’t sensitive enough. However, during the Apollo missions, seismometers measured thousands of tiny quakes on the moon.

The new lander, called InSight, was supposed to leave for Mars two years ago but at the last minute, mission engineers found that the lander’s most crucial instrument — the vacuum-encased seismometer — had a leak that let air through. The instrument is extremely sensitive and even the slightest bit of air can ruin its measurements. The seismometer has since been fixed and, now that our planet and Mars are aligned again, it will soon launch for its mission.

Technicians inspect InSight instruments. Credit: NASA.

Technicians inspect InSight instruments. Credit: NASA.

Marsquakes could teach scientists a great deal about Mars’ interior, how it formed, and what kind of changes it has incurred throughout its geological history. When a quake travels through a material, its vibration changes. Therefore, the vibrations picked up by a seismometer can be decoded to reveal information about the various layers the quake has passed through. The lander is also carrying radio antennas that will help scientists estimate the size of Mars’ core. Another instrument, a nail-like device, is designed to insert itself into the ground in order to measure the planet’s internal temperature — the kind of information that can help scientists figure out what fueled Mars’ ancient volcanoes. 

InSight scientists hope to record hundreds to thousands of small Martian quakes. Perhaps InSight will be able to answer some very important questions like why Earth is a habitable paradise and Mars is a cold and barren rock. So far, we’ve learned a lot about the Martian surface — now, it’s time to probe its deep interior.

Insight is set to launch on an Atlas V rocket, which will take off from Vandenberg Air Force Base in California on May 5th at 7:05 AM ET.

 

Scientists find evidence of 1755 earthquake in pond sediment

To this day, the Cape Ann 1755 earthquake remains the largest earthquake in the history of Massachusetts. According to existing data, no one was killed, but it damaged hundreds of buildings in Boston and was felt as far north as Nova Scotia and as far south as South Carolina. Now, seismologists have found evidence for this earthquake in the unlikeliest of places: a pond.

A layer of sediment told researchers quite a bit about an old earthquake. Image in public domain, not from actual study.

Katrin Monecke of Wellesley College and her colleagues were able to identify a layer of light brown organic-rich mud within the core, deposited between 1740 and 1810. They concluded that the unusual sediment comes from an underwater landslide, probably caused by the Cape Ann earthquake.

Earthquakes are not common in New England, which lies on the inside of a tectonic plate. Earthquakes are much more common in places like California, which lie at the edge of tectonic plates. With few geological faults or other telltale clues of the earthquake, seismologists have gotten a bit more creative in their search for evidence.

“We don’t have any evidence of the fault that ruptured in 1755 for several reasons: the earthquake was probably not large enough to cause a surface rupture. Also, based on historical description of damage, the epicenter of the 1755 earthquake was most likely offshore,” Monecke told ZME Science in an email.

“It is important to see what an earthquake signature looks like in these sediments, so that we can start looking at deeper, older records in the region and then figure out whether 1755-type earthquakes take place for example, every 1000 years, or every 2000 years,” she added.

Earthquake forensics

Sluice Pond was in the area most strongly hit by the earthquake, which is why it was selected. Earthquakes need to be quite strong to be able to see deformation within the lake sediment. It has steep sides that would make it more susceptible to a landslide, and it has deep undisturbed layers of sediment for coring. Land clearing by settlers may have made the lake more susceptible to shaking.

“These were our main indicators that something had happened in the lake. We saw these near shore sediments and fragments of near-shore vegetation that appear to have been washed into the deep basin [by strong shaking],” said Monecke.

“It is important to see what an earthquake signature looks like in these sediments, so that we can start looking at deeper, older records in the region and then figure out whether 1755-type earthquakes take place for example, every 1000 years, or every 2000 years,” Monecke added.

The results could help to calculate the age of sediments from other ponds. You can learn more about the variation in the sediments and what they mean by also being able to know approximately when they happen. It would be interesting to look at the effect of earthquakes on the land in other areas. Researchers want to use these results as a sort of calibration and find older horizons in sediments for other earthquakes.

“This study can be seen as the calibration of earthquake-induced deformation in lake sediments in this area. With this information, we can now target deeper sediments that accumulated in Sluice Pond since the glaciers left the area and date back to about 16,000 years ago. Finding older earthquake horizons within these sediments will allow us to determine the recurrence intervals of 1755-type earthquakes. We also look at other lakes in the area, for example Walden Pond. It is the deepest lake in eastern Massachusetts and we expect to find an excellent sedimentary record here, too,” Monecke added in an email.

Although intraplate earthquakes are much rarer, they still do happen. Although they’re much rarer, they can still be quite massive.

“Earthquakes can occur in intraplate tectonic settings where strain is accumulating but at much slower rates compared to plate boundaries. This slow accumulation of strain causes large earthquakes to occur but with much longer recurrence intervals in the order of centuries to millennia. It is possible that preexisting, ancient fault lines get re-activated during these earthquakes,” Monecke concludes.

“The 1755 Cape Ann earthquake recorded in lake sediments of eastern New England –an interdisciplinary paleoseismic approach,” by Katrin Monecke et al, was published in Seismological Research Letters.

Geologists listen to volcanic murmur to predict eruptions

A new study found that monitoring volcanoes for inaudible, low-frequency sounds might help predict dangerous eruptions.

Audible sounds and earthquakes have a lot in common with each other — after all, they’re both caused by acoustic waves. Sure, they’re propagating at different frequencies and through different mediums, but at their core, they’re similar waves. With a bit of artistic license, you could say that seismology is the science that “listens” to the Earth.

Well, researchers from Stanford and Boise State University now want to actually listen to a volcano. They found that by monitoring the infrasound detected by monitoring stations on the slopes of the Villarrica volcano in southern Chile, one of the most active volcanoes in the world, they could predict impending eruptions.

The sounds (vibrations) they were picking up were produced by the rumbling of a lava lake located inside the volcano’s crater. When the volcano’s activity intensifies, the lake starts to shake and stir, creating more sounds.

“Our results point to how infrasound could aid in forecasting volcanic eruptions,” said study co-author Leighton Watson, a graduate student in the lab of Eric Dunham, an associate professor in the Department of Geophysics of the Stanford School of Earth, Energy & Environmental Sciences. “Infrasound is potentially a key piece of information available to volcanologists to gauge the likelihood of an eruption hours or days ahead.”

Of course, many of the world’s big volcanoes are already being monitored. Seismic activity can be a good indicator of an eruption. The idea isn’t to replace it with infrasound, but rather to complement it, along with all other methods used for volcano monitoring. However, there are still significant challenges.

Villarrica is one of Chile’s most active volcanoes.

While thus far, the infrasound readings have proven quite reliable, they also need to be confirmed in other environments, on other volcanoes. It’s not clear to what extent this information can be used to anticipate eruptions and how reliable this data can be.

Furthermore, this has only been tested on “open vent” volcanoes like Villarrica, where an exposed lake or channels of lava connect the volcano’s inner fire to the atmosphere. Applying the same method on a closed volcano will undoubtedly prove to be much more difficult, or even impossible.

“Volcanoes are complicated and there is currently no universally applicable means of predicting eruptions. In all likelihood, there never will be,” Dunham said. “Instead, we can look to the many indicators of increased volcanic activity, like seismicity, gas emissions, ground deformation, and – as we further demonstrated in this study – infrasound, in order to make robust forecasts of eruptions.”

Journal Reference: Jeffrey B. Johnson, Leighton M. Watson, Jose L. Palma, Eric M. Dunham, Jacob F. Anderson. Forecasting the eruption of an open-vent volcano using resonant infrasound tones. DOI: 10.1002/2017GL076506

Earthquakes aren’t affected by moon phases nor by time of year, new study demonstrates

Researchers have debunked one of the most enduring myths about earthquakes: that they are influenced by the moon or the time of year. Susan Hough at the US Geological Survey found that the patterns which some have interpreted as a link between these phenomena are nothing more than jibberish: “the kinds of patterns you would get if the data are completely random.”

An unlikely culprit: the moon.

Shake, rattle, and roll

Mankind has been aware of earthquakes since time immemorial, but to this day, there are aspects of earthquakes we’ve yet to understand. The rumble and shake we feel at the surface is basically the release of energy coming from down below — from kilometers to tens or even hundreds of kilometers deep. This energy reaches us through seismic waves, a type of acoustic wave. In a way, you could say that earthquakes are the music of the Earth, but that music can be devastating.

An 8.6 magnitude earthquake, like the one that struck Chile in 2010, releases the same amount of energy as 10,000 atomic bombs of the kind used in World War II. Naturally, being able to reliably predict these events would be incredibly important, but this has proven impossible, and will likely continue to be impossible in the future. No, despite what some snake oil salesmen claim, no scientist has ever predicted a major earthquake. But this doesn’t mean that we can’t foresee some things about them.

Earthquakes are usually caused when rock underground suddenly breaks along a fault. Since the Earth’s crust is split into rigid plates which are constantly moving, there’s plenty of pressure to cause such events. What researchers can calculate is where this pressure is building up, and where earthquakes are more likely to strike in a certain timeframe. For instance, we know that a big earthquake is very likely to strike California soon — but we can’t predict exactly when and where it will strike. In other words, seismologists are looking at trends and patterns, not specifics.

Map of earthquakes in 2017. A total of 12,797 earthquakes are plotted. Credits: USGS.

This is why some have suspected that the moon might also play a role in earthquake formation. Simply put, the idea is that just like the moon causes tides, it could add a bit of extra pressure on the tectonic plates — just enough to cause an increase in seismicity. That idea spread even more after a 2016 study found that the San Andreas fault in California might be influenced by the lunar tides. Well, that theory just doesn’t stand, a new study reports.

Promise me the moon

Susan Hough analyzed 204 earthquakes of magnitude 8 or larger, correlating them with the time of year and the lunar phase. The analysis went back to 1600, and she focused on large earthquakes because they are certain to be “their own master” — not a result of an aftershock or other seismic events. It also gave her the opportunity to compare results with previous studies.

“A recent study … for example, concluded that very large earthquakes, with magnitudes close to 9, tend to occur near the time of maximum tidal stress,” Hough said in her study, adding that researchers “point out, however, that the relationship is not clear-cut and does not hold when low-magnitude events are included in the analysis.”

The theory seemed to make a lot of sense. It’s not that the moon puts great stress on the Earth. It’s just a little, but it might be that extra little that pushes things over the edge.

“In recent years, there have been a couple of nice studies that show that tidal forces do modulate earthquake rates slightly. It makes sense: the tides create stress in the solid earth, and not just the oceans. And in some cases, that small force can be ‘the straw that breaks that camel’s back’ and nudges the fault to produce an earthquake,” Hough said.

However, her data showed nothing — no correlation, no pattern, nothing that indicates a connection between earthquake occurrence and the moon or the time of the year.

This doesn’t mean that no patterns were observed. Data showed that most earthquakes took place seven days after the new moon — in a period where the moon’s attraction was lowest. This goes completely against the theory and only shows that it’s just a coincidence. It’s just like flipping a coin: sometimes you’ll get tails six times in a row, but that doesn’t mean anything.

“My statistical analysis showed that this apparent signal is not statistically significant,” Hough said. “But there’s so much lore about earthquakes and full moons; I was a little surprised that earthquakes have bunched up on a day about which there’s no popular lore.”

Image credits: Aaron Benson.

However, things are not finally settled. Hough’s analysis didn’t account for small earthquakes, and it is plausible that if the tidal stress does have an effect, you’re more likely to see it there. Also, 204 data points are far from ideal. In theory, the coincidence could swing the other way — the moon might be causing the earthquakes, but earthquakes also randomly happen during other days, masking the correlation. If anything, I’d expect this study to stir things up even more. The debate is far from settled.

“I’ve read Charles Richter’s files, the amateur predictors who wrote to him in droves, because he was the one person that people knew to write to … and if you read the letters, they’re similar to what people are saying now, it’s all the same ideas.”

“Sooner or later there is going to be another big earthquake on a full moon, and the lore will pop back up,” said Hough. “The hope is that this will give people a solid study to point to, to show that over time, there isn’t a track record of big earthquakes happening on a full moon.”

Journal Reference: Susan Hough et al. Do Large (Magnitude > 8) Global Earthquakes Occur on Preferred Days of the Calendar Year or Lunar Cycle? DOI: 10.1785/0220170154

Earth sunrise

The Earth whispers in a low hum that’s now been recorded for the 1st time underwater

Under the background of a never-ending racket bellowed by animals, human machines, and natural forces, the Earth itself is humming to a tune that only the sharpest mechanical ‘ears’ can pick up. For years, scientists have known that our planet produces a low-frequency drone. These subtle oscillations or seismic movements are far too minute to be called an earthquake, but they’re still measurable. Now, researchers report recording this distinct ‘hum’ for the first time underwater.

Earth sunrise

Credit: Pixabay.

Will you sing along?

People are justifiably terrified of earthquakes but the truth is the vast majority of tremors are totally harmless. Of the half a million or so earthquakes estimated to occur on a yearly basis, only 100,000 are strong enough to be felt and it’s just about 100 of these that can actually cause damage. 

There are murmurs that are even quieter. A ground-breaking paper published in the 1990s reported that the Earth is constantly busy with microseismic activity known as “free oscillation”. This constant vibration produces a hum that has been detected on land by special equipment known as seismometers. 

Scientists had been debating the source of this unusual and perpetual hum for some time until a 2015 paper determined that two marine factors are primarily responsible for the imperceptible planetary drone. The ebb and flow of ocean waves reaching the seafloor, and the vibrations caused by the collision of ocean waves add up to produce the hum.  The result is a strange ultralow frequency that resonates almost identically all over the planet.

Now, this hum has been recorded underwater for the first time. This is a great achievement, as three-quarters of the planet is covered in water and up until recently, we had no idea whether or not there was a difference. It turns out that the ultralow frequencies are the same on land as they are at the bottom of the ocean.

The findings were reported in the Geophysical Research Letters by a team led by Martha Deen, a geophysicist at the Paris Institute of Earth Physics. Her team employed a dataset collected from 57 free-fall seismometers deployed around La Réunion Island to the east of Madagascar. The instruments covered an area measuring about 772 square miles (2,000 square kilometers) and were deployed there to study volcanic hotspots. Deen and colleagues found they could study the planetary hum with the same data after cleaning it of noise like ocean currents or waves.

Impressively, the scientists “were able to reduce the noise level to approximately the same level as a quiet land station.”

The study determined Earth’s natural vibration peaks at several frequencies between 2.9 and 4.5 millihertz. That’s about 10,000 times smaller than the lower hearing threshold of the human ear, which is 20 hertz. When the signal was compared to measurements taken by land stations in Algeria, researchers found the two signals’ amplitudes were similar.

This planetary hum might actually prove practical in some endeavors. Scientists have often been able to exploit earthquakes to plot subterranean maps based on the predictable effect seismic waves have in the crust. Some believe this ultralow hum extends all the way to the core and could be used for similar purposes. Others have even wilder ideas like using an equivalent hum on alien planets to map their subterranean structure.

“Earth is constantly in movement, and we wanted to observe these movements because the field could benefit from having more data,” Deen told the AGU blog.

Let’s not get too carried away, though. We’re only beginning to understand what the deal is with Earth’s hum and how it could impact our lives. It’s, nevertheless, intriguing news to learn that this planet is never quiet. I like it restless.

No, seismologists aren’t really predicting dramatic earthquakes for 2018 — it’s a single hypothesis from one study, not a fact

Yesterday, headlines all around the world stopped just short of announcing impending doom. “Deadly earthquakes could hit a BILLION people next year because of Earth’s slowing rotation,” warned The Daily Mail. “Upsurge in big earthquakes predicted for 2018 as Earth rotation slows,” The Guardian also read. But that’s misleading at best, and fear-mongering at worst. Here’s why.

The hypothesis

The discussion was sparked by a presentation at the Geological Society of America’s meeting in Washington, USA. Roger Bilham of the University of Colorado (CU) in Boulder and Rebecca Bendick at the University of Montana in Missoula reported that during the past 100 years, Earth’s slowdowns have correlated surprisingly well with periods of increased seismicity — especially for large earthquakes, with a magnitude of 7 and over. Since Earth is starting a cycle of roughly 32 years where it will slightly slow down its rotational speed, Bilham and Bendick predicted an increase in earthquake frequency and intensity in 2018.

“The year 2017 marks six years following a deceleration episode that commenced in 2011, suggesting that the world has now entered a period of enhanced global seismic productivity with a duration of at least five years,” they concluded.

The idea is this slight deceleration, while changing the length of the day by only a millisecond, would still release a tremendous amount of energy, which could “fuel” the increase in earthquakes. Exactly why these slight decreases in day length are linked to earthquakes (or whether they have a common cause) is unclear.

The hypothesis didn’t come out of the blue. In a previous work published in August in Geophysical Research Letters, they reported that earthquakes tend to cluster up in time — not place — and that earthquakes seemed to peak at 32-year intervals, something which they believe connected to the Earth’s core. Most of the devastating earthquakes originate in the crust, relatively close to the surface (less than 30 km deep) so seismologists don’t usually associate the core with seismic events, but it is certainly plausible that the core also plays a role in the grand scheme of things. At the equator, Earth spins 460 meters per second. Even slight speed mismatches between the core and the mantle could generate enough energy to power earthquakes.

The connection is certainly significant and deserves investigation, says Peter Molnar, a geologist also at CU. However, “It might be nonsense,” Molnar adds.

The problem

A map of the earthquakes in 2017. If the theory is correct, the 2018 map will have many more orange and red dots.

Earthquake prediction is a loaded minefield. The sheer complexity of seismic processes makes it impossible to predict any individual earthquake. This doesn’t necessarily mean that general trends or patterns can’t be established. This is exactly what Bilham and Bendick went for.

“What we started with was the idea that maybe earthquakes are more like neurons or batteries, in the sense that they have a certain amount of time required that charges them up and gives them a potential to fail, and after that charging interval, they can fail at any time.” Bendick says.

Still, before we start panicking about “scientists predicting massive earthquakes in 2018,” there are a few things we must consider.

First, it remains to be seen whether their hypothesis passes scientific scrutiny. While it builds on previous work which has been verified, it remains to be seen whether these new ideas also pass the test. Secondly, while the correlation seems indeed strong, it does not imply causation. No underlying mechanism or causal link has been determined. Even if we do see an increase in earthquakes in 2018, it’s hard to say that the Earth slowing down is causing them. Furthermore, earthquake frequency varies due to many aspects, some of which we have yet to identify.

The study’s timeframe is also short. Since the cycle’s periodicity is at around 32 years, we’ve only had four peak years to spot a pattern. Statistical fluctuations can be large and there’s just not enough past data to say, with a satisfying degree of confidence, that this — increased seismicity — will happen in 2018. It’s certainly plausible, but just because it’s plausible doesn’t mean it will happen. If anything, it requires a leap of faith.

The takeaway

What Bilham and Bendick reported is an intriguing study. Personally, I think the world needs more of this “let’s see what’s happening here” studies — it’s a healthy approach which can lead to groundbreaking results. But the media often overreact when it comes to this type of research. Panic-inducing headlines catch on. Everyone wants a catchy angle, and real science often falls in the background. It remains to be seen whether the hypothesis stands the test of time or not. In the meantime, let’s not take “one study says this thing might happen” and turn it into “scientists predict disaster for billions of people,” shall we? That’s not only disrespectful, but also dangerous.

In the end, I think Bendick sums it up quite neatly:

“To me, this is a really fun and exciting and beautiful example of how science works,” Bendick says. “We put out this hypothesis, and two things are going to happen. One is that all of our colleagues are going to try to figure out why we’re wrong. That’s how it’s supposed to work. The other is that it’s a pretty bold forecast. By the end of next year, and certainly by 2020, we’ll have a solid test of the findings.”

New study confirms injections associated with oil and gas can cause earthquakes

A new study confirmed that oil and gas exploitation in the US can generate a surprising number of earthquakes.

A few decades ago, Oklahoma barely had any earthquakes. Nowadays, there’s a few hundred earthquakes magnitude 3 or greater every year, with over 800 such earthquakes in 2015. This is pretty bizarre and especially unexpected when you consider that all this is happening in the Great Plains, far away from the boundary of any tectonic plates and major fault. So what’s happening, then?

Oil and gas

Graphic representation of how hydraulic fracking injections work. Image credits: USGS.

In 2014, a study conducted by USGS geologists caused quite a fuss, concluding that wastewater injection associated with hydrocarbon exploration (oil and gas) caused a 5.0 earthquake near Prague, Oklahoma, and several smaller ones. A further study confirmed these concerns, finding that the average yearly number of earthquakes over the magnitude of 3 had gone up from 1 to 230. The connection between these earthquakes and hydrocarbon activities tightened in 2016 when a paper found a clear link between hydraulic fracking and the increased seismicity. There were clear signs that fracking has the potential to activate geological faults.

“This seismic event was caused by hydraulic fracturing,” Ken Paulson, CEO of the BC Oil and Gas Commission, said in a statement.

Aside from the things often discussed in relation to fracking, there’s also the problem of water. Hydraulic fracking, as the name implies, requires water — a lot of it. Water use per well can be anywhere from about 1.5 million gallons to about 16 million gallons, and fields tend to have hundreds of wells. In just two years, 8.8 billion gallons of wastewater were injected in Oklahoma alone. Faced with what was already an emerging crisis, authorities in Oklahoma have taken first steps to regulate wastewater injection and a reduction in earthquakes was reported — though there were still over 600 temblors in 2016.

But the improvement was slight at best. In September 2016, the Pawnee earthquake struck with a magnitude of 5.8. It was the strongest earthquake ever recorded in Oklahoma. Now, researchers from the Institut de physique du globe de Paris (IPGP) have just published a study on this earthquake.

The black culprit

The Pawnee earthquake broke a pre-existing fault within the crystalline basement located beneath the sedimentary cover (dashed line) where fluid injection is taking place. Institut de physique du globe de Paris (IPGP).

Analyzing seismological data recorded in the region of the Pawnee earthquake as well as seismograms acquired thousands of kilometers from the epicenter, they were able to detail how the rupture happened and how the seismic wave spread from the epicenter. They then combined this data with radar interferograms from the Sentinel-1 satellites of the European Space Agency (ESA), measuring the surface deformation induced by the earthquake.

By studying all of this, they concluded that the slip of the earthquake was 40 centimeters at most, while the epicenter’s depth is anywhere between 4 and 9 kilometers deep (when the epicenter is very shallow, its exact depth is almost impossible to deduct). At a first glance, this would indicate that there’s no connection between the hydrocarbon activities and the earthquake since wastewater injection takes place at 2 to 3 kilometers. However, at a deeper look, scientists found that this brings forth a much more worrisome conclusion: these injections can reactivate a seismic fault.

It’s not exactly clear how this happens, though two mechanisms are possible. Either the injection pushes other fluids outward, creating a pressure “wave” which reaches the geological fault and then causes critical pressure on a fault — even an inactive one. Another proposed mechanism is centered on the tendency of rocks to deform elastically over short time scales (from a few days to several months). Like a sponge, rocks can accumulate fluids, and then release them under stress, again potentially reactivating faults. The fact that injections can generate earthquakes not only locally, but also in remote places, is even more concerning.

A political fault

To make things even worse, we didn’t even know of the existence of this fault beforehand. Locating underground faults is extremely difficult, and the lack of knowledge of fault networks brings major risks. Previous studies have shown that the reactivation of such faults is not impossible even naturally — when you give them an extra boost (with hydraulic fracking, for instance), things can get worse faster.

But if you’ve made it thus far, then I have even more bad news. It’s not just the local geology and the oil & gas industry causing problems… it’s also the political environment. Even before becoming the head of the Environmental Protection Agency, Scott Pruitt has worked relentlessly in Oklahoma to oppose the installing of new environmental laws and even to support the removal of existing regulations. With his powers increasing and with the clear anti-environment stance president Trump has taken, it’s unlikely that things will get better anytime soon in Oklahoma, and other similar parts of the US. Adding the political factor into a puzzle which already includes a nasty industry, unknown faults, and earthquakes seems like a recipe for disaster.

Journal Reference: Raphaël Grandin, Martin Vallée, Robin Lacassin — Rupture Process of the Mw 5.8 Pawnee, Oklahoma, Earthquake from Sentinel‐1 InSAR and Seismological Data. DOI: 10.1785/0220160226.

New Zealand’s earthquake pushes the sea floor 2 meters above ground

A magnitude 7.8 earthquake shook New Zealand on Monday night and left the locals of Kaikoura, South Island with an incredible surprise: areas of the sea floor were thrust up to 2 meters above ground, pushing up through the sand in lumpy slabs.

It’s geology under our noses. The pieces of sea bed rose so fast, they were still teeming with ocean critters by the time locals realized what had happened — and scientists say they’ve never seen anything like it before.

“I’ve never seen it before during an earthquake and it’s the first time we’ve seen something like this,” marine geologist Joshu Mountjoy from New Zealand’s National Institute of Water and Atmospheric Research told Stuff.

“It will take a while before this becomes normal again.”

“Man I should really stop drinking on Mondays”– this little crab. Image credits Anna Redmond / Facebook

“Man I should really stop drinking on Mondays”– this little crab.
Image credits Anna Redmond / Facebook

The quake sadly took a heavy toll on central New Zealand however, with reports of over 1,000 locals and tourists stranded by landslides, dozens of injuries and two reported dead.

Mountjoy sais the effects were so dire because of a phenomenon known as co-seismic movement. Basically, two almost simultaneous quakes have acted on fault lines across the South Island just after midnight, concentrating their energy. The unique nature of the event is probably behind the striking sea-bed movement in Kaikoura, with some pretty wide areas rising almost two meters above their initial position. And it all happened in a few minutes.

Nicola Litchfield, Earthquake geologist and head of the Active Landscapes Department at GNS Science told Michael Daly from Stuff that these movements had to have happened during the 90 to 120 seconds the quake lasted.

“It would have been amazing if it had been daylight and someone had seen it,” she said.

Researchers are now working on determining how the coast changed after the quake, already suspecting that rocks moved not only vertically, but horizontally as well.

“It’s not just a single rupture on one fault plain, it’s ruptured multiple fault strands all along the coast there,” said Mountjoy. “So that uplift will reflect that behaviour of different faults.”

GPS station installed on the island have revealed that Cape Campbell in the Marlborough region has moved north-east by 2 to 3 meters, and the tide gauge at Kaikoura rose a whopping 90 centimeters. Given these dramatic movements, it will take a while before the full extent of the earthquake’s effects are understood.

 

Watch all the volcanoes and earthquakes since 1960 hit around the world in one app

The Global Volcanism Program has released an interactive map showing the three big E’s (earthquakes, eruptions, emissions) since 1960.

And it looks like this. Image credits Global Volcanism Program.

And it looks like this.
Image credits Global Volcanism Program.

For something literally set in stone, Earth’s crust is far from inactive.

The relatively thin layer of solid rock covering the planet is fractured into tectonic plates, which move relative to each other — bending, pushing, crashing together. This constant motion creates rifts, huge chasms in the crust where magma boils up to the surface to create new rock, and subduction zones where rocks sink and are melted down into fresh magma.

Tectonic processes release huge amounts of energy and matter, creating earthquakes and powering volcanism. Now, for the first time, a global visualization (link to app) of seismic and volcanic data lets us see the effects of the crust’s constant movements. The map was created by the Global Volcanism Program at the Smithsonian’s National Museum of Natural History, with data from the USGS and NASA. It tracks every recorded volcanic eruption (red triangle) and earthquake (blue circle) since 1960. Starting from 1978, satellite UV monitoring allowed scientists to pick up on sulfur dioxide emissions (yellow circle) in the atmosphere. You can see all the events at once, or let them add up as time passes. Clicking on eruptions after 1978 lets you watch it’s sulfur clouds appear and dissipate.

And, if you take the final image of E3s and stack them over a tectonic map, you’ll see just how well they stack with the edges of plates. Volcanoes, in particular, tend to follow their outlines — the ones inland usually revolve around hotspots such as those in Iceland, Indonesia, the Aleutian islands and the tip of South America. Earthquakes farther from the outlines are usually formed around fault or fault systems, or may simply be tremors.

 

What are tsunamis and how they form

Most waves form due to winds or tides, but tsunamis have a different cause altogether. A tsunami is most often formed by an earthquake, but it can also be formed by an underwater landslide, volcano eruption or even meteorite.

The process is fairly complex, so let’s start digging into it.

The Great Wave off Kanagawa, an artistic depiction of a tsunami by Katsushika Hokusai.

What is a tsunami

“Tsunami” is a Japanese word meaning “harbor wave,” but that doesn’t say much about their nature, and tsunamis are not nearly restricted to harbors. A more accurate term would be “seismic sea waves,” and it would describe them more accurately. However, tsunami has stuck and it’s what everyone uses today. People sometimes refer to them as “tidal waves,” but that term is technically incorrect and should be avoided in this context.

Tsunamis are indeed waves, but unlike wind waves, they have a much larger wavelength. Think a bit about waves — in the context of physics, not in the context of sea waves. A defining characteristic of every wave is its wavelength. Wind waves have short wavelengths which can be clearly seen on any shoreline. They come in every few seconds, with a few meters  in between — sometimes, even less. But a tsunami has a huge wavelength, oftentimes longer than a hundred kilometers and this is why they are so dangerous (more on that a bit later). Tsunamis are almost always not singular waves, but come in as train waves.

How tsunamis form – earthquakes

The vast majority of tsunamis form due to earthquakes — specifically tectonic tsunamis. As an earthquake happens, the ground beneath the water is moved up and/or down abruptly and as this movement happens, a mass of water is displaced and starts moving in all directions. This marks the start of a tsunami.

The displaced water starts to move as a wave. At this point, it has a very low amplitude as it is located in deep water (earthquakes on the coastline rarely cause tsunamis). Tsunamis in open water are usually shorter than 0.3 meters (12 inches).

 

Image by Régis Lachaume. Propagation of a tsunami offshore, showing the variation of wavelength and amplitude as a function of depth.

As the wave starts moving towards the shore, a series of events begin to occur. First of all, water gets shallower and shallower. As a result, the height of the tsunami starts to increase, and can increase dramatically. This is the main reason why these waves are so dangerous: They carry on huge masses of water. When they get closer to the shoreline, the volume of the tsunami remains constant, but because the water gets shallower, their height starts to increase.

The 3D simulation below shows how the process is taking place — note the waterline retreating before the tsunami hits. This is called a drawback.

 

Also, the shallow water somewhat slows down the waves and the waves start getting closer together. In the deepest parts of the ocean, tsunamis can travel faster than a jet, at 970 kph (600 mph). This means that in only a few hours, it can cross entire oceans.

Tsunamis don’t stop once they hit land. Much of their energy is dissipated and reflected back, but some of it is still maintained and tsunamis will continue to travel inland until all their energy is gone. So don’t think that if you’re a bit farther from the beach, you’re safe. In some rare instances, tsunamis can also travel up river valleys.

How tsunamis form — from other sources

In rare cases, tsunamis can also be caused by landslides, volcano eruptions, and meteorites. In all cases the main principle is the same — a water mass is displaced and as it nears the shoreline it starts growing in height. However, the displacement mechanism differs.

Landslide

Underwater, landslides are often similar to volcanoes that avalanche into the sea. This process happens as a result of an earthquake, so in a way, the main source is still an earthquake. However, earthquakes can also merely loosen landmass which starts falling at some later point.

Lituya Bay, Alaska, is an area prone to tsunamis (via Wikipedia).

Volcanoes

Volcanoes can form tsunamis through two mechanisms. Either they collapse or they eject matter with such strength that they uplift the water. In the first case, land-based volcanoes can also cause tsunamis, if they are very close to the sea.

Meteorites

If you’ve ever thrown a pebble into the water, you’ve seen that it creates ripples. The meteorite works in pretty much the same way, except it creates huge ripples. This kind of tsunamis are really rare, but there is an instance in 1958 where such a wave was created by rockfall in Lituya Bay, Alaska.

Why tsunamis are so dangerous

Tsunamis are not always colossal waves when they come into the shore. According to the USGS, “… most tsunamis do not result in giant breaking waves (like normal surf waves at the beach that curl over as they approach shore). Rather, they come in much like very strong and very fast tides (i.e., a rapid, local rise in sea level).”

By now, you should have a pretty clear idea why tsunamis are so dangerous. They can be very long (100 kilometers is a reasonable length), very high (the 2011 Japan tsunami measured over 10 meters) and can travel extremely fast without losing much of their energy. An earthquake far into the ocean can send several devastating tsunamis hundreds or even thousands of kilometers away.

2004 tsunami

A map of the 2004 tsunami with the highlighted epicenter.

In 2004, an earthquake with the epicenter off the west coast of Sumatra, Indonesia struck with a magnitude of 9.1–9.3. The Indian Plate was subducted by the Burma Plate and triggered a series of devastating tsunamis, some over 30 meters high. The tsunamis killed over 230,000 people in 14 countries, being one of the biggest natural disasters in human history. It is just one in many tragic examples highlighting the sheer force of tsunamis.

Safety for tsunamis

  • The first thing to do is to stay informed.

Since science cannot predict when earthquakes will occur, we cannot determine exactly when a tsunami will be generated. However, that doesn’t mean we’re clueless. With the aid of historical records of tsunamis and numerical models of their size and speed, we can get a pretty good idea as to where they’re likely to be generated. You should always know if you’re in a tsunami risk zone. An estimated 85% of all tsunamis have been observed in the Pacific Ocean in the “Ring of Fire,” but other areas can be dangerous as well and as we mentioned above, tsunamis can also travel great distances.

  • If you feel an earthquake in a low-lying, coastal area, keep calm and move away from the coast. Not all earthquakes cause tsunamis, but some do.
  • If you see a large water mass retreating, this is the drawback. It’s a telltale sign that a tsunami is coming. A 10-year-old girl saved many lives in 2004 because she knew this from her geography lessons.
  • Tsunamis are rarely singular waves — they come in packs, so if one hits, don’t think it’s ‘all clear’ – more may be on their way. Earthquakes also often have replicas, which in turn can cause tsunamis.
  • Be on the lookout for tsunami warnings. Tsunamis are fast, but they still take some time to travel. So if you know of an earthquake nearby, check a tsunami forecast and see what it says. Also keep in mind that a small tsunami on one beach can be a big one on a nearby beach. Underwater topography can play a massive role.
  • Buildings are no protection against a tsunami. Going farther away from the beach is the best thing you can do.
  • If you’re somehow on a boat or ship and there’s a tsunami coming your way, it may be smarter to move your ship farther into the ocean where the tsunami is smaller. However, this can be very risky. Stay tuned to your local radio, marine radio, NOAA Weather Radio, or television stations during a tsunami emergency.
  • Whatever you do, don’t purposely go to the beach to see a tsunami. Seriously. It will outrun or outdrive you and it’s not safe at all.

 

Italian earthquake kills at least 20, destroys entire town

A 6.2 magnitude earthquake struck north-east of Rome, wiping off the small town of Amatrice and killing at least 20 people in the process.

An aerial photo of Amatrice taken by the fire brigade showed the scale of the damage.

The epicenter was located 10km South East of Norcia, Italy, and roughly 120km from Rome/Vatican City area. It’s expected that Rome itself will be left unscathed, though many residents were given quite a scare. But not everyone was so lucky.

Dozens of mountain villages were devastated, including the town of Amatrice, whose mayor said that his town “isn’t here anymore”. So far, 21 fatalities have been reported, but as the earthquake struck at 3.36 AM, officials fear many more are still trapped under the rubble. Missing persons have been reported, and the authorities helped by locals are conducting searches for any survivors.

Sergio Pirozzi, the mayor in Amatrice, near Rieti, said that the city was packed with tourists, as the town is a popular destination during the summer.

“There are so many dead I cannot make an estimate,” he told RAI state television. “We have already extracted several dead bodies but we do not know how many there are there below. There are dozens of victims, many under the rubble. We are setting up a place for the bodies.”

Earlier he told the broadcaster: “Half of the town is gone.”

1492

Stefano Petrucci, mayor of Accumoli, near the epicentre, also expected dire news.

“Now that daylight has come, we see that the situation is even more dreadful than we feared with buildings collapsed, people trapped under the rubble and no sound of life.”

Italy is one of the most earthquake-prone areas in Europe. The last major earthquake to hit Italy struck the central city of L’Aquila in 2009, killing more than 300 people. Another major temblor struck in the Romagna region in May 2012, when two violent shocks 10 days apart killed 23 people.

Fracking is indeed causing earthquakes, new research finds

A survey of a major oil and natural gas-producing region in Western Canada founds evidence that hydraulic fracturing or “fracking” does indeed cause earthquakes in the region. The study, like several others before it, differs from reports by oil and gas companies, who claim fracking does nothing to increase local seismicity.

Illustration of hydraulic fracturing and related activities, via EPA.

Hydraulic fracking is the well-stimulation technique in which rock is fractured by a pressurized liquid. It sounds harmless enough, but fracking causes a myriad of problems. For a single well, millions of gallons of water, sand and chemicals are pumped inside, without a strict control of the resulting fissure system. Aside for the huge water consumption, other environmental problems include air emissions and climate change, water contamination, land use, risk of earthquakes, noise pollution, and health effects on humans. To be honest, among those, the risk of earthquakes doesn’t rank particularly high because the resulting earthquakes are generally very small – but it’s definitely a risk you don’t want to ignore.

This study, which was published in Seismological Research Letters, analyzed oils in the Western Canada Sedimentary Basin (WCSB) which contains one of the world’s largest oil and gas reserves, and is dotted with thousands of fracking wells drilled in multi-stage horizontal operations. Gail M. Atkinson of Western University analyzed the relationship of 12,289 fracking wells and 1236 wastewater disposal wells to magnitude 3 or larger earthquakes in an area of 454,000 square kilometers. The numbers are certainly large enough to offer statistical relevance.

The researchers performed a statistical analysis to figure out which earthquakes could be caused by hydraulic fracking. Basically all the earthquakes in the area were caused by humans. More than 60% of these quakes are linked to hydraulic fracture, about 30-35% come from disposal wells, and less than 10% come from natural causes.

“It had previously been believed that hydraulic fracturing couldn’t trigger larger earthquakes because the fluid volumes were so small compared to that of a disposal well,” Atkinson explained. “But if there isn’t any relationship between the maximum magnitude and the fluid disposal, then potentially one could trigger larger events if the fluid pressures find their way to a suitably stressed fault.”

Atkinson and colleagues found 39 hydraulic fracturing wells (0.3% of the total of fracking wells studied), and 17 wastewater disposal wells (1% of the disposal wells studied) that could be linked to earthquakes of magnitude 3 or larger. These are small percentages, but when you consider that thousands of these wells are being drilled every year in Western Canada alone, the scale of this problem becomes evident. So far, there has been no significant damage caused by these earthquakes, but it seems like only a matter of time before this happens.

“We haven’t had a large earthquake near vulnerable infrastructure yet,” she said, “but I think it’s really just a matter of time before we start seeing damage coming out of this.”

It’s important to note that oil and gas companies have long downplayed the risk of seismicity caused by hydraulic fracking. Researchers warn that better and more impartial ways of estimating this risk have to be developed.

Journal Reference: http://dx.doi.org/10.1785/0220150263

Tsunami Warning Lifted After Magnitude 7.8 Quake Off Indonesia

Indonesian authorities lifted a tsunami warning issued after a magnitude 7.8 earthquake struck off the island of Sumatra – the largest earthquake since the 2004 disaster.

The U.S. Geological Survey said the epicenter was about 500 miles west-southwest of Padang, Indonesia and 529 miles north-northwest of the Cocos Islands. Source: USGS

“There is no info on casualties or damages yet,” Sutopo Purwo Nugroho, a spokesman at the national disaster mitigation agency, said via text message. “The tsunami warning is based on modeling, while tsunami buoys in Indonesian waters haven’t reported any existence of a tsunami. Many buoys are broken and not functioning, so we don’t know whether the potential for a tsunami in the waters is true or not.”

According to the United States Geological Survey, the earthquake struck at 19:49 local time (12:49 GMT). It said the epicentre was 805km (500 miles) south-west of the city of Padang, and 24km deep.

Thankfully, there seems to be no damage caused by the earthquakes and any tsunamis should have already hit by now, so the coast seems to be safe for now. Telephone communication was reported to be down in the Mentawai island chain, which is closer to the epicenter.

The tectonics of Indonesia are very complex, as it is a meeting point of several tectonic plates, which makes it one of the most active earthquake hotspots in the world. In 2004, a massive 9.1 magnitude earthquake struck Indonesia, with the resulting tsunami killing 230,000 people in 14 countries, and inundating coastal communities with waves up to 30 metres (100 ft) high. It was one of the deadliest natural disasters in recorded history.

Did North Korea actually test a bomb? Science actually has the answer

North Korea recently announced that it tested a massive H-bomb, one that’s “capable of wiping out the entire United States”. While the latter is certainly not true, there is reason to believe that that they did test some kind of bomb. How do we know? Science.

Bombs and Earthquakes

Image via Wikipedia.

According to the Treaty on the Non-Proliferation of Nuclear Weapons, commonly known as the Non-Proliferation Treaty, no country is allowed to test nuclear weapons. But in order for that treaty to function, we need a way to verify it. You may be surprised to hear that the answer is “seismology” – we know when nukes are tested by studying earthquakes.

Basically only North Korea is testing nuclear weapons at this point. Image via Wikipedia.

Whenever an earthquake takes place, waves start propagating. There are three main types of waves: P (primary), S (secondary) and Surface Waves. P waves are pressure waves formed from alternating compressions and dilations propagating longitudinally. When an earthquake strikes there is both compression and dilation around the focal mechanism, but when a bomb strikes, all the force is blasted around the impact, creating only compressions.

“As the bomb is detonating, it’s compressing the rock immediately adjacent to it, and that propagates out to the recording stations” as Pwaves, said Douglas Dreger, a seismologist at the University of California, Berkeley. The first wave to reach the seismometer generates an “up” signal. Seismologists use the term “up” because the ground actually moves up when the compression phase of a P wave arrives and the squeezed underground rock and soil juts upward at the surface.

Image via Wikipedia.

Researchers plot the up and down signals from the P wave on black and white diagrams called focal mechanism plots. These plots can indicate the direction in which the wave is traveling after a shock, and would be half black and half white for earthquakes. In the case of bombs, they’re completely black – and this was the case for Korea.

Seismology can’t know what type of Bomb it is

So, through seismology, we know that North Korea did test a bomb. We can also calculate the magnitude the earthquake. This explosion, coming in at 5.1 magnitude is likely below the magnitude a hydrogen bomb would produce, said Brian Stump, a seismologist at Southern Methodist University in Dallas, Texas.

But this is where the uncertainty pops in. There are two types of nuclear bombs: A-bombs and H-bombs and the difference between them is highly nuanced. Broadly speaking, A-bombs are fission weapons that create smaller explosions – of “only” equivalent to tens or hundreds of thousands of tons (kilotons) of TNT. H-bombs are fusion boms that can reach up to tens of millions of tons (megatons) of TNT.

A-bomb vs H-bomb comparison. Image via Wikipedia.

Now again, speaking simply, you can have bigger A-bombs and smaller H-bombs. You can have an H-bomb that does create fusion, but for which most of the energy comes from non-fusion sources; is it still an H-bomb? Some would argue that yes, some would argue that no. You can’t know without conducting radioactivity measurements. But since North Korea conducted their test underground, all the radiation is trapped and we can’t know.

The conclusions

Image via Wiki Commons.

So, North Korea definitely tested some kind of bomb — we know this with a great degree of certainty. It may have been a small fusion bomb, a larger fission bomb, some hybrid bomb or something completely different; we can’t know for sure at the moment. You can usually class everything North Korean officials say under “hogwash” but they probably did test an H-bomb. Just not the kind of H-bomb most people are thinking of.

Largest man-made Earthquake comes after fracking activity

A new unfortunate world record has been triggered by fracking. A 4.6 magnitude has struck in northern British Columbia in August 2015, but only now has the investigation concluded.

“This seismic event was caused by hydraulic fracturing,” Ken Paulson, CEO of the BC Oil and Gas Commission, said in a statement.

Hydraulic fracking is the process of injecting pressurized fluids in an oil or gas well in order to fracture the rock and facilitate extraction. Hydraulic fracking is highly controversial and already banned in several countries. Its proponents advocate the economic benefits of more extensively accessible hydrocarbons, but there is mounting evidence that the environmental damage heavily outweighs the benefits.

Aside for possible water contamination, surface spills and massive greenhouse gas emissions, there is also a growing risk of seismicity. Fracking has the potential to activate geological faults and we already know that it caused a cascade of Oklahoma earthquakes. Earlier in 2014, we were reporting a study that concluded that two earthquakes with a magnitude of over 5 were caused by humans, as a result of oil exploration. In 2008 the average number of earthquakes with a magnitude over 3 was 1 – just one significant earthquake a year. But after fracking commenced, there were over 230 such earthquakes.

Magnitude 3 earthquakes don’t pose much of a threat themselves, but they are a clear indicator that something is happening. When 4.6 earthquakes start happening, that’s a very different story. Earthquakes magnitude is measured on a logarithmic scale, so magnitude 4 is 10 times larger than magnitude 3. According to CBS News, locals felt this quake, which was described by Canada seismologist Alison Bird as “significant.”

Since August when it occurred, there was a very good chance it was a case of induced seismicity, but a formal investigation was set up to determine whether this was the case – and it was. At this point it’s not clear what will happen in the future and whether fracking will continue “business as usual” or something will change.

This glacier produces half a million ice quakes a year

Somewhere in the Arctic, in the interior of the Greenland ice sheets, there lies a glacier like no other. This glacier quakes once every minute, more frequently than ever observed. Geologists now believe that studying these ice quakes could help them better understand how ice melts and reacts to rising temperatures and better model ice flow.

Researchers work in Greenland to instill seismic activity detectors, buried into glacier sediment.
Credit:Timothy Bartholomaus

It’s only natural that as temperatures continue to rise across the globe, ice starts to melt. But while we know that very well, we’re still struggling to quantify exactly how and when that is happening. As glaciers melt, they also slide and budge, and this glacier motion could help us understand the short-term factors that contribute to the larger scale motion of glaciers, according to Timothy Bartholomaus, a glaciologist at the University of Texas.

“To make better predictions of how ice flow is going to occur in the future, we have to have that mechanistic understanding of how ice flows now,” Bartholomaus said.

He and other researchers from the University of Texas Institute for Geophysics and the University of Kansas have detected over one million icequakes produced by a single Greenland glacier named Kangerlussuup Sermia, or KS for short. Their findings were reported at the fall meeting of the American Geophysics Union (AGU). They explain that while many glaciers quake, none has been observed to do so at this frequency.

“This is not something that has been seen at other glaciers,” Bartholomaus said. “Other glaciers produce seismic signals, but not nearly this frequently.”

KS itself spans over 100 kilometers from the interior of the Greenland Ice Sheet to the Western coast. In order to study it seismically, the team placed three soup-can sized seismometers close to it in 2013, and have been recording data ever since. They believe the seismic activity can be correlated somehow with the amount of water coming out of the glacier.

“A hundred years ago seismologists knew not to put seismometers by rivers because they’re noisy and make it hard to study earthquakes. But now scientists are turning that logic on its head and saying maybe we can learn more about rivers through seismometers,” says Bartholomaus in a previous report. “We can do the same thing with glaciers. And now, for the first time, track subglacial discharge by looking at tremor.”

The seismometer sensor is buried underground, with surface – supplied batteries, GPS, and solar panels to record timing of icequakes.
Credit:Timothy Bartholomaus

Of course, tectonic earthquakes are fundamentally different from icequakes in a number of aspects; tectonic quakes are generally much stronger, and don’t happen as often and as regularly as icequakes do.

“You can imagine that glaciers are flowing down under the influence of gravity, and there are various factors that are holding them back, so they don’t just zip along at Mach speeds,” he said.

Estimating the rate at which ice melts is vital for future predictions, especially as it’s not just about ice melting directly. Some basins are held in place only by small chunks of ice, just like wine in a bottle is held by a cork. So even slight warming and melting could cause significant sea level rise. This melting rate could be the difference between Miami being a sunny vacation destination or an urban swamp.

“We’ve known for decades the glaciers are melting and sea level is rising. But there is still uncertainty regarding what controls how fast it’s happening,” says Bartholomaus. “Is sea level rise going to remain constant or will the rate double? We’re trying to bat down that uncertainty.”

Italy’s earthquake scientists have finally been cleared

I’m happy to say that one of the most absurd events in modern science has finally concluded, and with a normal result. The Italian seismologists tried with manslaughter for not carrying a good enough risk analysis have been cleared – most of them, at least.

TheWiz83 /Wikimedia Commons

The L’Aquila earthquake struck in central Italy on 6 April 2009 with a magnitude of 6.3, killing 309 people and injuring more than 1,500. The area had been previously struck by a swarm of smaller earthquakes, and a committee was called to evaluate the risk. The seven researchers – three seismologists, a volcanologist, and two seismic engineers ultimately told the public that the chance of danger hadn’t increased or decreased and that there was no apparent reason to be worried. However, judge Marco Billi, called their work a “superficial, approximate and generic” risk analysis. Billi explained that the scientists were not guilty of failing to predict the earthquake, but failing to “discharge their duties under the law,” a decision which made waves around the world.

Initially they were convicted and sentenced to jail, then acquitted, and then the prosecution asked for their sentences to be reinstated. After a 10-hour closed door hearing, the five-judge panel delivered their verdict – they completely cleared six of the scientist, and greatly reduced the sentence of the seventh. The main defence for the scientists was that their work was solid, but the problem was that Bernado De Bernardinis, the seventh scientist assured the public that there is no reason to worry.

The scientific community was appalled by the initial verdict, that scientists can be sentenced for not having success in their research, and this decision came with a major sigh of relief. UK seismologist Ian Main from the University of Edinburgh told Nature last year:

“We don’t want to have to be worried about the possibility of being prosecuted if we give advice on earthquakes. That would discourage giving honest opinion.”

8.3 Magnitude Earthquake strikes Chile

A massive 8.3 magnitude Earthquake struck the northern coast of Chile on Wednesday night, killing at least five people and causing buildings to sway in the capital city of Santiago. Following the earthquake, waves of up to 4.5 meters were reported in some areas of the coast. About one million people were evacuated.

The earthquake’s epicenter. Image via USGS.

“I was in an open area on the ground, in Santiago when the initial earthquake stuck. It was so strong that I could barely stand on the ground and saw buildings around me sway. It was very long as well, and I felt as if the ground itself would break apart. Till now, at around 5:30 AM, there have been more than 30 after shocks,” local Sumit Kaul said through Guardian Witnesses.

The aftershocks were also massive; there are reports of one measuring 7.0 and at least three over 6.0.

“Once again we must confront a powerful blow from nature,” President Michelle Bachelet said, addressing the nation late Wednesday.

Damage in Chile. Image via The Malay Mail.

Chile, a country used to strong earthquakes, reacted promptly and evacuated over a million people from the 2,400 miles (3,900 kilometers) coast of Chile’s Pacific shore.

Some adobe houses have also collapsed in Illapel, and there is no thorough estimation at the moment. In the city of Coquimbo, mayor Cristian Galleguillos said the city was starting to see flooding and 95% of the city had lost electrical power. All the inhabitants were evacuated before the waves hit the city. Pictures from a nearby mall showed significant destruction.

Tectonics

According to a preliminary assessment from the U.S. Geological Survey, the earthquake’s epicenter was about 54 kilometers (34 miles) west of Illapel; the temblor occurred as the result of thrust faulting on the interface between the Nazca and South America plates in Central Chile. Chile has a long history of massive earthquakes, including the 2010 8.8 earthquake which ruptured a ~400 km long section of the plate boundary.

Most of the large earthquakes in South America (and especially in Chile) occur close to the surface, of depths smaller than 20 km; they are the result of both crustal and inter-tectonic plate deformation. The South American arc extends over 7,000 km, from the Chilean margin triple junction offshore of southern Chile to the offshore areas of Panama. Since 1900, numerous massive earthquakes have been recorded on this subduction zone, often followed by devastating tsunamis. The largest earthquake ever recorded, the 1960 M9.5 earthquake was also recorded in the Chile area.